The present invention relates to a rear vehicle-body structure of an automotive vehicle which comprises a rear floor panel and a pair of right-and-left rear side frames extending in a vehicle longitudinal direction and connected to both side portions, in a vehicle width direction, of the rear floor panel.
Generally, a pair of right-and-left rear side frames which extend in a vehicle longitudinal direction are provided at a rear vehicle-body portion of an automotive vehicle for the purpose of ensuring the vehicle-body rigidity.
In recent years, reducing of the weight and thickness of the rear side frame has been attained by using a high-tensile steel plate, so that the bucking performance of the rear side frame deteriorates because of the thin plate-thickness and also breaking of the rear side frame or peeling of a welding portion improperly occur because of the high tension. Consequently, it has become difficult to control load-absorption and deformation of the rear side frame.
Meanwhile, in a torsion-beam axle type of rear suspension in which no sub frame is provided below a rear floor panel, the rear side frame cannot be supported by the sub frame, so that the rear side frame is configured in a cantilever manner such that it extends rearward from the vicinity of a floor kick-up portion at a central side of a vehicle body. Accordingly, it is difficult to stabilize buckling deformation of the rear side frame. It is basically desired that the above-described rear side frame can surely absorb a collision load by its being bent (folded) at plural points in order from its rear-end side, being supported firmly at its base-end side (a central side in a vehicle longitudinal direction).
Japanese Patent Laid-Open Publication No. 2013-233898 discloses a structure in which a pair of right-and-left rear side frames extending in the vehicle longitudinal direction are provided below a rear floor panel and beads are alternately formed at both sides of the rear side frame which are spaced apart from each other in the longitudinal direction. Herein, the beads can be points to cause bucking of the rear side frame when a collision load is inputted to the right-and-left rear side frames from a rear bumper beam in a vehicle rear collision.
The above-described patent document, however, does not disclose nor remotely suggest anything about a longitudinal distance between the above-described beads as a bending-promotion portion.
Meanwhile, Japanese Utility-Model Laid-Open Publication No. S55-147971 discloses a structure in which a vertical bead extending in parallel to an axial direction of a frame is formed at a rear end portion of the frame and a lateral bead extending perpendicularly to the axial direction of the frame is formed at a front portion of the frame.
However, this patent document does not disclose nor remotely suggest anything about forming of plural lateral beads and a longitudinal distance between the plural lateral beads.